Famous Alvin Sub Waits for Lithium-Ion Battery Pack

By · May 28, 2013

Alvin on deck

Alvin on the deck of the research vessel WHOI R/V Atlantis in Woods Hole. A trip to the west coast, and another three years of scientific exploration, is imminent. (Jim Motavalli photo)

No, it doesn't look much like an electric car, but there are some remarkable parallels. The famous deep-sea submarine Alvin, which explored deep-sea vents and the wreck of the Titanic, has made 4,600 dives and remains a state-of-the-art submersible despite its 1964 construction date. Alvin, owned by the Navy and operated by the Woods Hole Oceanographic Institute (WHOI), has just undergone a $41 million upgrade that will allow it to reach 6,500 meters and explore 98 percent of the ocean’s floor.

Back in Action

Alvin's robot arms

Alvin hydraulic robotic arms pick specimens off the ocean floor. (Jim Motavalli photo)

Alvin was sitting in its custom-made “garage” on the Woods Hole, Massachusetts-based WHOI R/V Atlantis research vessel last week, shortly before a trip to the West Coast and its first exploratory dives this summer. Scientific research will start up again in the fall if everything goes well.

Alvin has the latest technology in every area but one—its battery pack. Like a 1909 Detroit Electric, Alvin is powered by lead-acid batteries. Those batteries, which weigh 3,500 pounds, power everything from the reversible thrusters that the Alvin uses to navigate to the exterior lights.

According to Susan Humphris, a WHOI senior scientist who headed the Alvin’s renovation, “To go to 6,500 meters, we’re going to need a new battery system. We’re looking at lithium-ion, but since the Boeing Dreamliner issue came up we’ve been pursuing more research to ensure that we can package those cells in a safe way.”

Of course, many of these same safety challenges apply to Boeing’s planes. Li-ion batteries are inescapable, because of their energy density and lower weight, but volatility remains a serious issue, especially in critical applications such as Alvin.

Replacing the battery pack is a high priority as part of Phase II of the submarine’s upgrade. According to Humphris, “We’re hoping we’ll be able to upgrade the pack within five years. It remains a big question.” Here's a closer look at the Alvin on video:

Big Advantages to Lithium

Yes, the same flammability issue that grounded the Dreamliners is holding up deep-sea diving in the Alvin. But li-ion has so many advantages (including a 500-pound weight cut) that the engineers are working overtime to come up with a safe solution. According to Daniel Gomez-Ibanez, a WHOI engineer, the plan is to double Alvin’s battery capacity, from 40 to 80 kilowatt-hours, with more than 10,000 individual cells.

Gomez-Ibanez is still waiting for the go signal to begin work on such a lithium-ion pack, but in the meantime he’s clear about how the batteries will have to perform.

“It’s a lot of energy in a small volume, and there’s the potential to release that energy in a short amount of time,” Gomez-Ibanez said. “Anyone who says the technology is fundamentally safe is being overly optimistic. But sending a submarine down 6,000 meters is not inherently safe, either. You have to accept some residual risk.”

How It Could Work

The battery issues the WHOI engineers are grappling with are essentially the same safety concerns that automakers have faced and overcome in going electric. Gomez-Ibanez identifies four key priorities:

  • The batteries will be partitioned so a small, localized fire won’t spread to adjacent cells. “If one neighborhood burns you don’t want it to engulf the whole city,” Gomez-Ibanez said.
  • Cells will have to be assembled under extremely clean conditions, with strict controls on all the manufacturing steps. “It’s difficult, because usually the cells aren’t made just for you,” Gomez-Ibanez said. “They’re usually made in large quantities by someone else.”
  • In operation, cells have to be closely monitored so temperature and other variables remain within safe limits.
  • Positioning is vitally important. “You can’t put anything extremely life-critical next to the batteries,” Gomez-Ibanez said. “No proximity to any systems that could compromise the structure or floatation.”

With li-ion, Alvin should be able to explore whole new realms of the deep ocean floor. With lead-acid, it will be business as usual. By the way, Gomez-Ibanez may be convinced of the benefits of li-ion, but he's no big fan of the electric car. "I don't have one, and I don't see the benefits at this point," he said. "They're too expensive and complex. I ride a bicycle."

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